That is because they opposed Allah and His Messenger. And whoever opposes Allah - then indeed, Allah is severe in penalty.
The Saheeh International Quran Translation
ذَٰلِكَ بِأَنَّهُمْ شَآقُّوا۟ ٱللَّهَ وَرَسُولَهُۥ وَمَن يُشَآقِّ ٱللَّهَ فَإِنَّ ٱللَّهَ شَدِيدُ ٱلْعِقَابِThat is because they opposed Allah and His Messenger. And whoever opposes Allah - then indeed, Allah is severe in penalty.